The invention relates to a heatable cutting device, in particular, scissors, a knife, a hair-cutting apparatus or the like, with a cutting blade with an electric heating element for the heating process, and with an electric connection for operating the electric heating element by means of an electric voltage supply device.
Heatable cutting devices, in particular, heatable scissors for cutting hair have the advantage that the hair is cauterized by the hot cutting blades during cutting. This means that the hair ends lightly melt. The hair ends, therefore, are practically sealed and this counteracts spit ends.
A heatable cutting device in the form of heatable scissors of the aforementioned kind is known from WO 92/00688. The basic idea is to arrange a separate cutting element, made of metal and having a front cutting edge, to a blade holder defining a base body. For this purpose, the blade holder is provided with a recess into which the cutting element is inserted and secured by screws tot he blade holder. A separate heating foil is provided between the blade holder and the cutting element. The heating foil is supplied with current by an electric voltage supply device. The resistor element heats up the cutting element. The disadvantage of these known heatable scissors lies in the arrangement of the heating element in the form of a separate heating foil which has to be arranged between the blade holder and the actual cutting element. It is a disadvantage that moisture can very easily penetrate which can lead to destruction of the heating foil. Also the assembly of the heatable scissors is cumbersome.
Another type of heatable scissors is disclosed in DE-U-295 06 308. Here, the cutting blade is protected at its exterior side by a plastic cover. Between this plastic cover and the actual cutting blade, a heating foil is arranged which is also a separate member. The great disadvantage of this known heatable scissors is that moisture can very easily penetrate into the space between the cutting blade and the plastic cover, and, sooner or later, this will lead to destruction of the heating foil. Accordingly, these heatable scissors are associated with a high failure rate.
Another problem with all known heatable scissors is that the cables for electrically connecting the scissors to the electrical voltage supply frequently break. This means that the scissors have to be entirely disassembled for their repair in order to insert the cable. This is obviously cumbersome and costly.
The scissors may be any kind of scissors, for example, hairdresser""s scissors, tailor""s scissors, household scissors, poultry scissors, paper scissors, a hedge-trimmer etc. Such scissors, in general, have two cutting blades which are provided at the rear end with an actuating grip with openings for the fingers. In the transition area between the cutting blades and the actuating grips, the cutting blades are attached so as to be rotatable about a pivot axis relative to one another. This pivoting structure is formed by a screw which serves as a pivot axis. The problem with such scissors is that the pivoting structure has a relatively high frictional resistance so that the scissors are hard to actuate. This is particularly disadvantageous where the scissors are used for delicate and accurate cutting as, for example, at a hairdresser""s, since scissors that are easily to actuate are required here.
It is an object of the invention to create a heatable cutting device with an improved design of the electric heating element and an improved design for handling.
As a technical solution, the invention suggests that the electric heating elements are permanently and fixedly attached to the cutting blade.
The advantage of an accordingly designed heatable cutting device is that the electric heating element is integrated into the cutting blade by an undetachable, permanent, and fixed arrangement so that an overall compact unit of cutting blade/heating element is created. Because of the fixed attachment of the heating element at the cutting blade, the heating element is essentially encapsulated, and, in comparison to known heating foil arrangements, it is less accessible to penetrating moisture and, thus, less likely to corrode. The great advantage of the inventive heatable cutting device lies in its high operational reliability with a long service life without operational failure. The voltage supply of the electric heating resistance is provided by a suitable electric control device. In order for the cutting blade to have the desired temperature, a temperature sensor for an exact temperature measurement is advantageously also provided in the heating area. Just like the heating element, the temperature sensor can also be fixedly attached to the cutting blade. Alternatively, it is also conceivable that the temperature sensor is positioned separately on the cutting blade. This temperature sensor is also connected to the control device.
A preferred embodiment suggests that the electric heating element is being printed, sintered, or glued onto the cutting blade. Other application possibilities are conceivable. Especially, printing represents the preferred attachment of the electric heating element to the cuffing blade. In this case, no heating foil is used. Instead, the heating element is applied to the cutting blade by thick layer technology. In particular, the electric heating element is being applied by screen-printing. This means that a current-conducting paste is printed on, i.e., is applied and subsequently fired Such a heat conductor can have a thickness of 4 micrometers. This is sufficient to bring the cutting blade to the desired temperature.
A further development of this design suggests that the electric heating element is formed as a line along the cutting edge of the cutting blade. The heating element is, thus, embodied as a thin line extending along the cutting edge at a spacing and parallel thereto.
Advantageously, the cutting blade is made of metal or ceramic. Particularly a cutting blade made of ceramic distinguishes itself by a long service life with respect to its sharpness.
A further embodiment of the inventive cuffing device suggests that the cutting blade is supplied with electric voltage. In this event, the cutting blade is made of an electrically conducting material, namely, metal. However, it is equally conceivable to provide a ceramic cutting blade with a suitable metal layer which has the necessary electrical properties. While the cutting blade is supplied with electric voltage, an electrical stimulation of the scalp is possible during the hair cutting process. All that is necessary is to connect the body to the other pole of the current supply so that corresponding current runs through the hair.
A preferred embodiment suggests that the cutting blade is arranged at a base body as a separate member. The advantage of this is that the heating element can be attached to the cutting blade in a simple manner. The cutting blade being prepared in this manner can then be attached to the actual base body of the cutting device, e.g., glued, riveted or bolted to it. Preferably, the base body is provided with a corresponding recess into which the cutting blade can be inserted.
The base body can be made of plastic or ceramic. Plastic is the preferred material because a plastic base body can be manufactured in a simple injection-molding procedure.
Alternatively, it is also conceivable that the base body is made of metal. In this event, conventional metal scissors can be used. The only requirement for inserting the cutting blade in the base body is to provide a corresponding recess in the cutting blade area into which the separate cutting blade with the integrated heating element can be inserted and attached to.
Preferably, an insulating member is arranged between the base body and the cutting blade. This insulating member serves as a heat insulation as well as an electric insulation of the hot and electrically charged cutting blade with respect to the metallic base body. It is thereby warranted that the actual base body of the cutting device does not heat up and that the risk of bums is prevented.
A further embodiment in this context suggests that the base body is provided with an actuating grip, whereby a heat insulation is provided in the area between the base body having the heated cutting blade and the actuating grip. This can be accomplished in the case of the metal scissors in that the metal is being removed in this area and is substituted by plastic. A heat conduction into the actuating grip is thereby largely prevented so that additional protective mechanisms in the area of the actuating grip are not needed.
A further preferred embodiment suggests that an electric plug connection is provided at the cutting device for a connecting cable of the electric voltage supply device of the electric current supply of the heating elements. The basic idea is that the connection cable of the electric voltage supply device does not directly lead to the heating element, but instead contact is made by an electric plug connection. The electric plug connection can be effected by a plug/socket. Thus, the electric plug connection is fixedly integrated into the cutting device. The advantage of this is that the connection cable can be exchanged quickly and easily when it breaks without the necessity of, e.g., disassembling the entire scissors, including the heating element.
Preferably, the electric plug connection is provided within the actuating grip. This is a technically simple solution in order to be able to connect the connection cable to the electric plug connection. In the case of heatable scissors, the electric plug connection can be provided, in particular, in the area of one of the finger openings.
Furthermore, it is suggested in another embodiment that the cables leading from the electric plug connection to the electric heating element are provided within the body of the cutting device. This has the advantage that the cables do not interfere. In the case of scissors, the cables are provided in the grip area.
A further embodiment suggests that the cutting device is a scissors with two cutting blades which are rotatable toward each other about a pivoting axis via a pivoting structure having a roller bearing. The advantage of such scissors, provided with a roller bearing, is that the scissors are significantly easier to actuate in comparison to conventional scissors because the roller bearing decreases the frictional resistance. The term xe2x80x9croller bearingxe2x80x9d is to be understood as a descriptive term which includes all such bearings which decrease the frictional resistance between two parts that are being moved. In particular, roller bearings include ball bearings, sleeve bearings and needle bearings.
A preferred embodiment of the inventive scissors suggests that the roller bearing is provided with an outer ring and an inner ring which is concentric and rotatable in relation to the outer ring, the outer ring being fixedly connected with one of the cutting blades and the inner ring with the other cutting blade. Thereby, a technically simple option is created to decrease the frictional resistance between the two cutting blades by means of the roller bearing, the roller bearing rings being each associated with one of the two cutting blades. Thereby, the two roller bearing rings are connected to the two cutting blades such that they respectively rotate together. This can be achieved directly by having the corresponding roller bearing ring directly contact the corresponding cutting blade. However, an indirect connection is also conceivable, e.g., by providing intermediate means between the roller bearing ring and the cutting blade associated therewith.
A further embodiment suggests that the pivoting structure is provided by a bolt, penetrating an aligned bore between the two cutting blades, and a nut. This represents the conventional technical realization of a pivoting structure for scissors.
A further development suggests that the roller bearing is arranged at the outer surface of one of the cutting blades, the outer ring being fixedly connected to this outer side of the cutting blade and the inner ring being fixedly connected to the bolt or the nut. The basic idea of this roller bearing arrangement is, thus, that the roller bearing is not being positioned between the two cutting blades but that the roller bearing is associated with one of the cutting blades. The connection of the roller bearing with the other cutting blade is accomplished by the penetrating bolt which is indirectly connected to the other cutting blade.
A development of this embodiment suggests that a head of the bolt or of the nut rests externally at the inner ring. Thereby, the fixed connection is created by means of the bolt or the nut. The bottom side of the head can be slanted such that it only rests against the inner ring, but not against the outer ring.
A further development thereof suggests that the roller bearing is inserted into an exterior recess of the cutting blade by press fit. Because of this press fit, the fixed connection of the outer ring of the roller bearing to one of the cutting blades is created. This press fit is sufficient to securely hold the roller bearing because scissors have a relatively low pivoting force.
A further development suggests that the head covers the recess. Preferably, the head covers the recess in a sealing manner. Thereby, the antifriction bearing is protected from contamination and thus keeps its easy workability.
In an alternative to the earlier described arrangement of the roller bearing, it is finally suggested that a ring consisting of balls or needles is arranged between the two cutting blades concentrically about the pivoting axis. This means that the surfaces of the cutting blades facing each other directly slide on these balls or needles